We propose to maintain the overall goals of the program outlined by studying the following: 1) The mechanisms of hypercalciuria induced by diuretic drugs - as studied by micropuncture and microperfusion studies in rats and isolated perfused tubules. 2) The specific intratubular and extratubular mechanisms whereby phosphate infusions acutely lower phosphate excretion. 3) The urinary mechanisms whereby changes in calcium ionic concentration alters certain urinary proteins and facilitates their precipitation and/or toxicity.